Messages in this thread | | | From | Ilya Dryomov <> | Date | Tue, 27 Nov 2018 11:17:26 +0100 | Subject | Re: [PATCH V2] libceph: fix use after free |
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On Tue, Nov 27, 2018 at 10:22 AM Pan Bian <bianpan2016@163.com> wrote: > > The function ceph_monc_handle_map calls kfree(old) to free the old > monitor map, old points to monc->monmap. However, after that, it reads > monc->monmap->epoch and passes it to __ceph_monc_got_map. This will > result in a use-after-free bug. The patch moves the free operation after > the call to __ceph_monc_got_map. > > Fixes: 82dcabad750 ("libceph: revamp subs code, switch to SUBSCRIBE2 protocol") > > Signed-off-by: Pan Bian <bianpan2016@163.com> > --- > V2: correct the format of the tag Fixes > --- > net/ceph/mon_client.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/net/ceph/mon_client.c b/net/ceph/mon_client.c > index 18deb3d..05ef5aa 100644 > --- a/net/ceph/mon_client.c > +++ b/net/ceph/mon_client.c > @@ -478,9 +478,10 @@ static void ceph_monc_handle_map(struct ceph_mon_client *monc, > } > > client->monc.monmap = monmap;
monc->monmap is assigned here. It's not obvious, but monc->monmap and client->monc.monmap is the same pointer.
> - kfree(old); > > __ceph_monc_got_map(monc, CEPH_SUB_MONMAP, monc->monmap->epoch);
ceph_monmap_decode() returns the new map, kfree() frees the old map. I don't see a use-after-free here.
Thanks,
Ilya
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